The present invention relates to a hot air towel warmer and more particularly to an improved hot air towel warmer.
As pointed out in U.S. Pat. No. 6,046,436, whose patentee is the same as the applicant of the present application, the feel of a uniformly warm towel against the skin immediately after a shower or a bath is a delight that is only rarely enjoyed. If enjoyed in ones home before the inception of the hot air towel warmer of U.S. Pat. No. 6,046,436, it was only because one has managed to complete a shower shortly after having run a load of towels through the washer and dryer.
Experience has shown that the pleasure of a warm towel against the skin is diminished as the distance from the tub or shower to the towel warmer increases. Therefore, to be commercially viable, a towel warmer must be aesthetically pleasing and space economical while simultaneously satisfying the uniform building code which disallows duplex outlets close to tubs or showers.
An object of the present invention is to provide a safe, permanently installed towel warmer which is more desirable and user friendly since it can be placed in close proximity to a tub or shower thereby satisfying the uniform building code requirements which disallow duplex electrical outlets in close proximity to tubs or showers as a precaution against electrocution when live portable electrical appliances are inappropriately used, or dropped into occupied tubs or showers containing standing water.
Permanently installed electrical devices, such as lights, area heaters and exhaust fans do not have the same proximity restrictions, since they cannot be physically displaced into the tub area, and it is an object of the present invention to satisfy the safety criteria by the same approach.
Another object of the present invention is to prevent the possibility of igniting the towel in the unlikely event of short circuit failure of the primary temperature sensor, or heater coil power sequencing switch.
A rarely occurring but recognized failure mode of triacs is an electrical short from anode to cathode. Similarly, relays have been known to fail by self fusing the contacts to create an electrical short circuit. Since either a triac or a relay is required to allow the control electronics to modulate power to the heating element and thereby control the temperature within the antechamber, the present invention provides a thermal circuit breaker, or a bimetallic temperature sensor/switch located within the antechamber, (thermal accumulator/supply plenum) with a switch temperature (approximately 300xc2x0 F.) above the level maintained by the control electronics, but below the ignition temperature of cotton. This switch will in all likelihood never be activated during the entire lifetime of the towel warmer. Its sole purpose is to prevent towel ignition in the unlikely event of a short circuit failure of either the temperature control sensor, or power switch (triac or relay) which sequences the heater coil on and off to control air temperature.
The ultimate purpose of the disclosed towel warmer is to uniformly heat a towel to a predetermined end temperature within the short time duration of a typical shower (about 7 to 10 minutes) without any possibility of scorching the towel. To do so one must take advantage of the established thermodynamic principle which states that the rate of heat transfer (dH) from a warmer to a cooler body is in direct proportion to the temperature difference (dT) between the bodies and in inverse proportion to the distance between the bodies (D), stated mathematically: dH=K (dT/D). The disclosed towel warmer is configured to control two simultaneous heat exchange interactions; one between the electric heating coil and the return ambient air passing through it, and the second between the heated air within the towel heating chamber and the cotton fibers within the towel.
A further object of the present invention is to maintain the greatest possible dynamic temperature differential and the smallest possible heat path (distance) in each of these exchange interactions in order to maximize the actual rate of heat flow between the heater element and the individual towel fibers and thereby to minimize the time required to heat the towel.
Still a further object of the present invention is to reduce the overall size (volume) of the entire towel warmer enclosure such that the unit can be inconspicuously installed in bathrooms so designers, or remodeling contractors, can complete installation without impacting either the room esthetics, or the available counter space.
A feature of the present invention is the provision of a hot air towel warmer comprising a substantially air tight enclosure having a sealable access means to enable placing a towel and the like to be warmed in the substantially air tight enclosure and to enable removing a warmed towel therefrom; first means disposed within the substantially air tight enclosure having air passages therethrough to support the towel; second means disposed within the substantially air tight enclosure adjacent the first means to create a stream of air and to continuously circulate the stream of air within the substantially air tight enclosure for passage through the first means and the towel; third means disposed within the substantially air tight enclosure adjacent the second means to heat the stream of air; fourth means disposed within the substantially air tight enclosure associated with the stream of air, the second means and the third means to automatically maintain the stream of air at a temperature within a predetermined temperature range for a given period of time; and fifth means disposed within the substantially air tight enclosure associated with the stream of air, the third means and the fourth means to detect a short circuit in either one of the third means and the fourth means to prevent towel ignition in the unlikely event of such a short circuit.
Another feature of the present invention is the provision of a hot air towel warmer comprising a substantially air tight enclosure having a sealable access means to enable placing a towel and the like to be warmed in the substantially air tight enclosure and to enable removing a warmed towel therefrom; first means disposed within the substantially air tight enclosure having air passages therethrough to support the towel; second means disposed within the substantially air tight enclosure adjacent the first means to create a stream of air and to continuously circulate the stream of air within the substantially air tight enclosure for passage through the first means and the towel; third means disposed within the substantially air tight enclosure adjacent the second means to heat the stream of air; fourth means disposed within the substantially air tight enclosure associated with the stream of air, the second means and the third means to automatically maintain the stream of air at a temperature within a predetermined temperature range for a given period of time; and fifth means associated with the substantially air tight enclosure to enable permanent installation of the hot air towel warmer within a bathroom in close proximity to a selected one of a tub and a shower such that the hot air towel warmer is incapable of being displaced into a selected one of a tub and a shower.